Diesel engine analyzer



March 31, 1970 R, GERMANN ET AL 3,593,255

DIESEL ENGINE ANALYZER 5 Sheets-Sheet 1 Filed April 7, 1969 .@E. EcEQw. EN. EN 0.55

March 31, 1970 R, GERMANN ET AL 3,503,255

DIESEL ENGINE ANALYZER Filed April 7, 1969 5 Sheets-Sheet 2 March 31, 1970 R GERMANN ET AL 3,503,255

DIESEL ENGINE ANALYZER Filed April 7. 1969 5 Sheets-Sheet 5 March 31, 1970 R GERMANN ET AL 3,503,255

DIESEL ENGINE ANALYZER Filed April '7, 1969 5 Sheets-Sheet 4.

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March 31, 1970 R. GERMANN ET AL 3,503,255

DIESEL ENG INE ANALYZER 5 Sheets-Shawl*l 5 Filed April 7, 1969 United States Patent O 3,503,255 DIESEL ENGINE ANALYZER Reimar Germanu and Kurt Wiederwohl, Graz, and Martin Schwertfuhrer, Vienna, Austria, assignors, by mesne assignments, to Mobil Oil Corporation, New York, N.Y., a corporation of New York Continuation-impart of application Ser. No. 587,096,

Oct. 17, 1966. This application Apr. 7, 1969, Ser.

No. 822,809 Claims priority, application Austria, Sept. 27, 1966,

A 9,063/66 Int. Cl. G01m 15/00 ABSTRACT F THE DISCLOSURE A system is disclosed for synchronizing displays of diesel engine fuel injection pressures on an engine oscilloscope with engine operation. The fuel injection pressures are detected by transducers, and signals representative of the pressures are transmitted to the oscilloscope. The fuel injection pressure signal to one of the cylinders is used to drive a motor at a rate which is proportional to the speed of the engine, and the motor drives a device for generating vertical and horizontal synchronization input signals to the oscilloscope for synchronizing the display of the fuel injection pressure signals with engine operation.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of application Ser. No. 587,096, filed Oct. 17, 1966 and no-w abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention is directed to an analyzer for diesel engines. More particularly, this invention is directed to a method and a system for providing a display on an oscilloscope of the pressure patterns in the fuel injection lines to the cylinders of a diesel engine.

DESCRIPTION OF THE PRIOR ART In analyzing the condition and performance of diesel engines it is necessary to display and examine the pressure at each cylinder. Preferably, this analysis is made by a comparison between the individual pressures of a multicylinder engine. In such a display the position of the individual pressure curves to each other must be ascertained as a function of the engine crank shaft. This is often accomplished by installing triggering devices directly on the engine, either of a photoelectric or electromagnetic pickup type. An example of such a device is disclosed in Patent No. 3,243,997, by A. E. Traver. As disclosed in this patent the synchronization means includes three timing generators which include magnetic pickup devices attached to a rotor which is driven by or in synchronization with the engine crank shaft.

A disadvantage of conventional analyzers is that attachments must be made to the engine or its auxiliary devices in order to coordinate analyzer signals with `engine movement or cylinder position. This necessitates timeconsuming procedures and often introduces inaccuracies unless skillfully made. This difficulty has been a major obstacle to the wide-spread use of oscilloscope engine analyzers.

SUMMARY OF THE INVENTION The method and system according to the present invention synchronizes engine analyzer displays representative of fuel injection line pressures of a multi-cylinder dlesel engine with engine operation. Signals representative of the fuel injection line pressures are generated and supplied to the engine analyzer. One of the fuel injection line pressure signals is used to generate vertical and horizontal synchronization input signals to the engine analyzer, and the fuel injection pressure line signals are displayed on the engine analyzer in sychronization with engine operation in response to the vertical and horizontal synchronization signals.

In accordance with an aspect of the present invention, the fuel injection line pressure signal of one of the injection lines is used to drive a motor at a speed proportional to the speed of the engine, and the motor actuates means for generating vertical and horizontal synchronization input signals to the engine analyzer.

Thus, the present invention provides a method and system for synchronizing fuel injection line pressure displays on an engine analyzer without the necessity of a mechanical linkage between the engine or its auxiliary devices and the analyzer. Further, the present invention provides a method and a system for analyzing diesel engines which can be readily used with a wide variety of diesel engines and conventional analyzer scopes.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE l is a block diagram of the engine analyzer system.

FIGURE 2 is a detailed view of the trigger disk of FIGURE l.

FIGURE 3 depicts the nature of the synchronizing signal developed in the embodiment of FIGURE l.

FIGURES 4 and 5 present the system of FIGURE 1 in greater detail.

FIGURE 6 is an alternative embodiment of the engine analyzer system of this invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS In FIGURE l, a series of quartz pressure transducers, 10, 11, 12, are shown for attachment to the cylinders or fuel injection lines of a diesel engine. The broken line between transducers 11 and 12 indicates that a series of such transducers may be used. The number of transducers is equal to the number of cylinders in the engine -being analyzed. These quartz pickups may be installed in conventional adaptors for pressure measurements in the fuel injection lines. Pressure applied to the pickup causes its sensitive element, a quartz crystal, to generate an electrical charge proportional to the applied pressure. Suitable source follower amplifiers, 13, 14, 15 are associated with the respective pickups. The broken line between amplifiers 14 and 15 indicates the presence of additional amplifiers, one for each pressure pickup. These amplifiers change the signals generated by the high impedance transducers into low impedance signals which conform to the input signal requirements of Oscilloscopes. The signals from the source follower amplifiers are transmitted by a differential amplilier 16 to the Y (vertical) input of a conventional engine analyzer oscilloscope 17. An example of a suitable oscilloscope is the DuMont engine scope Model 901 (instruction manual copyrighted 1956).

The following arrangement is used for obtaining Signals which are used to synchronize the resultant oscillogram with the engine. The signals described below I-XIV, refer to FIGURE 3 and the corresponding points in the schematic of FIGURE l.

A signal is picked up by the quartz transducer 10 at one of the cylinders, for example, in the fuel injection line of the rst cylinder via a source follower amplifier 18, similar to that referred to above. A signal is transmitted to a phase inverter 19 which emits a signal I. Signal I is modified in the trigger level adjuster 20 to provide a suitable signal II to actuate Schmitt trigger 21.

The Schmitt trigger delivers a square wave of constant amplitude III which controls a monostable vibrator 22, This monostable vibrator delivers at its ouput a square pulse IV of constant amplitude and constant duration which controls a bi-stable switching stage 23 which emits square waves pulses V with an implse frequency equal to one half of the speed of the diesel fuel injection pump. This signal is then integrated at 24, tov provide signal VI, which is then decoupled at 25, and appears as signal VII. The frequency of the signal is then doubled at 26, which provides signal VIII with a frequency equal to the speed of rotation of the injection pump, but its amplitude is dependent upon frequency. The signal is decoupled at 27 to produce a signal IX which is then modified in trigger level adjuster 28 to provide signal X which actuates Schmitt trigger 29. The Schmitt trigger produces a constant amplitude square wave signal XI the impulse frequency of which is equal to the speed of rotation of the injection pump. This signal is amplified at 30 to produce a signal which actuates one phase of synchronous motor 31.

Three-phase synchronous motors having a synchronous starting require a capacitor connected between the two phases. The required speed range of 200-2000 r.p.m. corresponds to a frequency ratio of the supply voltage of 1:10. As the current in the windings of the motor has to remain constant with all speeds of rotation the capacitance has to be changed according to the frequency of the supply voltage (the impedance of the capacitor connected to the two phases would be 1/ w wherein w is 2r times the frequency and c is the capacitance). This would have to be done by switching between speed ranges.

In order to avoid this disadvantage in operating the device, the second phase of the synchronous motor is fed with a square wave which in comparison to the rst phase is displaced by 90. This is accomplished in FIG- URE 1 by transmitting signal XI to integrator 32 to produce a triangle wave signal XII. The triangle wave volta-ge is then decoupled with regard to DC voltage and modified by a trigger level adjuster 33 to provide a signal XIII to control a Schmitt trigger 34. The output of the Schmitt trigger is a constant amplitude square wave signal XIV which is amplified at 35 to provide a signal for the second phase of synchronous motor 31. The motor is shown grounded at 36. The speed of synchronous motor is exactly proportional to the speed of the diesel engine.

The synchronous motor 31 drives a coupling 37 on which a disk 38 is attached. Details of this disk are shown in FIGURE 2. This disk, preferably transparent, contains a series of trigger marks, 39, 40, 41, 42, 43. These trigger marks appear in graduated circumferences on the face of the trigger disk. Note that within the various circumferences there are respectively 1, 2, 4, 6 and 8 trigger marks. Pivotally attached at the center of said disk are brackets 44 and 45. These brackets independently scan the 360 circumference of the trigger disk. A graduated scale 46 on bracket 45 and a reference mark 47 on bracket 44 indicate the relative positions of said brackets. A locking nut 48 is provided to secure the relative positions of said brackets, while enabling them to'pivot as a unit.

Photosensitive devices 501, 502, 503, 504 and 505 are fixed on bracket 45 adjacent the respective circumferences 43, 42, 41, 40 and 39. Photosensitive devices 506i, 507, 508 and 509 are fixed on bracket 44 adjacent the respective circumferences of trigger marks 40, 41, 42 and 43. These photosensitive devices are actuated by their respectively positioned trigger marks (in conjunction with lights 49 and 50, positioned behind the trigger disk, shown only on FIGURES 5, discussed below). Signals from the photosensitive devices on bracket 44 are transmitted to four-way switch 51. The signal from one of the four photosensitive devices is transmitted through the switch to Schmitt trigger 52 and in turn to differential circuit limiter 53 which provides an actuating signal for stroboscope 54. The signal from this differential circuit limiter is also transmitted through gating switch 55 to differential amplifier 16 and oscilloscope 17.

The signals from the four outermost photosensitive devices on lbracket 45 are transmitted to four-way switch 56 and then to Schmitt trigger 57, amplifier 58, and then to oscilloscope 17 at the X-synchronization input point. The signal from photosensitive device 505 is transmitted to Schmitt trigger 59, amplifier 60 and then to oscilloscope 17 at the Y synchronization input point.

This device operates as follows. As referred to above the quartz transducers generate signals representative of the pressure patterns at the cylinders of the engine being examined. These pressure patterns are displayed on the oscilloscope by transmission to the Y input. In order to provide a signal for picture and line synchronization the foregoing invention was developed.

The synchronization signal is provided from one of the quartz pressure transducers. The signal is modified as set forth above and drives a synchronous motor with a frequency which is exactly proportional to the speed of rotation of the fuel injection pump. In turn this motor drives a trigger disk also at a rate proportional to the speed of rotation of the injection pump.

The trigger position for picture and line synchronization is taken at the innermost graduated circle on the circumference of the trigger disk. At this innermost point there is only one trigger mark 39 which actuates photosensitive device 505 to transmit a pulse once during each rotation of trigger disk 38. This pulse provides synchronization for the Y input to the oscilloscope once during each complete revolution of the trigger disk. In this manner the pulse for the series of transducers is repositioned once during each cycle through the transducers.

The remaining four series of trigger marks, and their corresponding photosensitive devices on bracket 45, serve for scanning the line synchronization pulses for 2, 4, 6, and 8 cylinder engines. By means of switch 56 signals may be transmitted Ifrom photosensitive device 501, 502, 503 or 504, which in turn generate either 8, 6, 4 or 2 signals for each complete rotation of disk 38. The number of pulses per rotation of disk 38 is chosen to correspond with the number of cylinders in the engine being examined.

When this device is put into operation, the signals on the oscilloscope may be in any position with regard to the time axis. By turning bracket 45 the total picture can be brought into the proper position. In order to coordinate the lines for the respective cylinders a switch 61 is placed between one of the transducers and the oscilloscope, for example, in the line 'for transducer 10. By actuating switch 61, thereby disconnecting the signal from transducer 10, the signal from cylinder l can be located among each of the cylinders displayed on the oscilloscope. By revolving bracket 45 the number 1 cylinder, for example, can be coordinated to appear on the first line of the oscilloscope.

The function o-f bracket 44, with the photosensitive devices positioned thereon, is to provide a signal indicative of top dead center for a selected cylinder in the engine. In a manner similar to that described above photosensitive device 506, 507, 508 or 509 generate either 2, 4, y6 or 8 signals for every complete rotation of trigger disk 38. The selection of the appropriate- Afrequency is made through switch 51 in accordance with the corresponding number of cylinders in the engine being examined. The signals from the photosensitive devices control the flashing of the stroboscope and therefore by movement of bracket 44 the stroboscope can be synchronized with the top dead center line on the engine flywheel. Therefore, the signal added through switch 55 will indicate on the oscilloscope the crank shaft position.

When brackets 45 and 44 are displaced by exactly 180, the line synchronization pulses and the synchronization pulses for the stroboscope coincide. By turning bracket 44 relative to bracket 45 the top dead center mark at the flywheel of the engine is brought to coincide with the fixed mark at the engine block. At the same time the top dead center mark gated in at the differential amplifier is shifting so that the start of injection at any time can be determined in degrees of movement of the crank shaft on the oscillogram. Moreover, the angle by which bracket 45 was turned relative to bracket `44 gives the start of injection directly in degrees of the crank shaft. This can be read from pointer 47 and scale 46 positioned respectively on bracket 44 and bracket 45. As the phase position of the trigger disk changes slightly with the changing speed of the injection pump, the entire oscillogram will move on the oscilloscope screen. To correct for this tendency the relative positions of brackets 44 and 45 are fixed by means of locking nut 48 after adjustment of the top dead center mark. Thereafter, `by turning coupled brackets 44 and 45 as a single unit the oscillogram can -be positioned on the screen of the oscilloscope, while maintaining the correlation between line synchronization pulses and top dead center marks during variation of the injection speed.

In an alternative embodiment (not shown) bracket 44 may contain only a single photosensitive device, for example, on the innermost circumference corresponding to the position of 505. In this embodiment a single pulse would be generated for each revolution of trigger disk 38, and only a single top dead center pulse would be produced on the oscillogram. This embodiment would obviate the need for switch 51. Alternatively, this reference pulse may be generated from a second disk, or other means. This pulse is for reference purposes and therefore may be varied to meet needs.

The electrical components described are conventional and may `be `found in a number of sources, such as the Transistor Manual, General Electric Company, 6th ed., Reference Data for Radio Engineers, International Telephone and Telegraph Company, 4th ed., and other standard works. An embodiment for several of these components is shown below, however, it will be appreciated that numerous electrical designs could be derived within the scope of the above disclosure.

FIGURES 4 and 5 present a more detailed embodiment of the system of FIGURE 1. Like numbers in FIGURES 1, 2, 4 and 5 refer to like components. In FIGURES 4 and 5 the letter C refers to condensers, and the letter R refers to resistors. The values of these condensers and resistors can readily be chosen by one skilled in the art to match the requirements of this system.

FIGURE 4 shows the means for the development of the signal to drive the synchronous motor. FIGURE 5 shows the means lfor the generation of the signals which are displayed on the oscilloscope. In FIGURE 4, the signal from transducer 10 is directed to the base of field effect transistor 305. The output from transistor 305 is connected through the indicated resistors and condenser to transistor 306 which serves as a phase inverter. As indicated the potential across the transistor is +18 volts and -6 volts. Throughout these drawings, arrows are used to indicate connections to power supply lines. The output of 306 is connected through the indicated rectifier diode 401 and condersers and resistors to the trigger level adjuster comprising the indicated variable resistor 201. The clipped signal from the trigger signal adjuster actuates Schmitt trigger 21, which in turn is connected to monostable vibrator 22 and bi-stable vibrator 23. A condenser is shown in the circuit for the monostable vibrator. Each of the major elements, 21, 22, and 23, is of conventional circuitry and is available as an on-the-shelf unit. The signal from the bi-stable vibrator23 is connected through transistor 307, an emitter follower, to the indicated condensers which integrate and decouple the signal.

CII

The frequency of the signal is then doubled by passage through transistor 308 and parallel coupled condensers and diodes 402 and 403 as indicated. The signal from transistor 309 is then modified at the .following indicated condenser to remove the D.C. component. The signal is further modified through transistor 310, and a trigger level adjuster which includes the indicated variable resistor 202. The signal from Schmitt trigger 29 is conducted through emitter follower 311 and integrated at the following indicated condenser. The signal is then conducted through 312 and the DC. component is removed. The signal is clipped at a trigger level adjuster, variable resistor 203, which actuates Schmitt trigger 34. The signals from respective Schmitt triggers 29 and 34 are modified in Darlington follower circuits 317, 318, 313 and 314; and further through variable resistors 204, 205 and Darlington amplifier circuits, which include 319, 320, and 315, 316. The signals are then smoothed through integrating condensers and decoupled of their D.C. components, which provide smoothed signals to operate synchronous motor 31. Note that the third phase of the synchronous motor is grounded.

The synchronous motor drives trigger disk 38 (see FIGURE 5) through coupler 37. Light sources 49 and 50 are disposed on one side of trigger disk 38 in position to activate photosensitive devices `501-509, each of which is respectively coupled to resistors and to selector switches 56 and 51. The output of switch 56 is connected through emitter follower 324 to activate Schmitt trigger 57, the signal from which is amplified through transistors 325 and 326. The output of 326 is connected to the x synch of oscilloscope 17. The signal from diode 505 is conducted through follower 321 to activate Schmitt trigger 59, the signal from which is amplified transistors 322 and 323. The output from 323 -is connected to the y synch of the oscilloscope 17. The signal from switch 51 is conducted through follower 327 to activate Schmitt trigger 52. The signal is then differentiated, rectified at diode 404 and conducted through follower 328 and a variable resistor 206 to the stroboscope 54 and amplifier 16.

The pressure transducer 101 in FIGURE 5 transmits a signal fromy the first cylinder to field effect transistor 302 connected to a base drain circuit, which includes trimmer condenser 102 which is grounded. The output of transistor 302 is transmitted through the indicated condenser and then through the phase adjuster switch 61 to the differential amplifier 16. Similarly, the signals from transducers 11 and 12 are conducted via the field effect transistors 303, 304 and the indicated condensers to the common line input of amplifier 16. The trimmer condensers 103, 104 are arranged as is 102 for the purpose of individual adjustment of the signals. This circuit arrangement is duplicated for each of the other transducers, 62, 63, 64, `65 and 66 shown in the figure.

Note that throughout this description conventional resistors and condensers whose function and position are clearly indicated in the figures were not specifically described. Additionally, the common lines from the power unit `67 which provide voltages of -12, -6, +12, +18, +80, are indicated merely by arrows, rather than by lines which would unduly complicate the drawing. Although the values of the condensers, resistors, diodes and transistors are not specifically set forth, these would be obvious to those skilled in the art and may be varied in accordance with the particular circuit designed to carry out this invention.

FIGURE 6 depicts an alternative embodiment of a means to drive the trigger disk of FIGURES 1 and 2. The signals from the quartz pressure transducers are directed to source follower amplifiers, the differential amplifier, and then to the y input of the engine scope, as set forth in FIGURE 1. In the embodiment of FIG- URE 6, a synchronizing signal is picked up from quartz pressure transducer 10" to drive a D.C. motor 68 which in turn is linked to the trigger disk of FIGURES 1 and 2.

The signal from 10 is amplified over a field effect transistor circuit 18 and conducted through a phase inverter stage 19. The signal'is modified over an adjustable trigger level, including Variable resistors 207, and conducted to a Schmitt trigger 20 which at its output delivers a square wave of constant amplitude to control a monostable vibrator 21. This monostable vibrator delivers at its output a square pulse of constant amplitude and constant duration. A pulse duration of 25 ms. and a pulse spacing of 5 ms. has been found suitable for the 400 to 4000 r.p.m. speed range of conventional diesel engines. The circuit depicted secures constant pulse durations which are unaffected by disturbances in line Voltage. The integrator and rectifier circuit following this stage, which includes rectifier diode 405, delivers at its output a D.C. voltage proportional to the speed of the engine. Transistors 329 and 330 comprise a Darlington circuit which is an impedance transformer stage, the output of which is conducted to an amplifier stage, transistor 331. A voltage feedback' through variable resistor 208 improves the stability of this circuit. The D.C. motor is diagonally connected to a bridge circuit formed by the transistors 332 and 333. The bridge is balanced at the base of transistor 333 by means of a Voltage divider which includes variable resistor 209. The speed of rotation of `this D.C. motor is a linear function of the supply voltage, which in turn is a function of the signal from quartz pressure transducer 10.

This invention has been described in terms of specific embodiments set forth in detail, but it should be understood that these are by way of illusrtation only and that the invention is not necessarily limited thereto. Alternative constructions will become apparent to those skilled in the art in view of this disclosure, and accordingly modifications of the apparatus and process disclosed herein are to be contemplated within the spirit of this invention.

We claim:

1. A method of displaying fuel pressures in the fuel injection lines of a diesel engine on an engine analyzer oscilloscope, wherein thefuel pressure displays are synchronized with engine rotation, comprising the steps of:

generating signals representative of fuel pressures in the fuel injection lines of the engine,

displaying said fuel pressure signals on said oscilloscope,

generating vertical and horizontal synchronization signals in response to one of said fuel pressure signals, and

synchronizing the displayed fuel pressure signals with engine rotation in response to said vertical and horizontal synchronization signals.

2. The method of claim 1 generating in response to said one fuel pressure signal a pulse train comprising a number of pulses corresponding to the number of cylinders, and applying said pulse train to said oscilloscope to display a representation of crank shaft position.

3. The method of claim 1 further comprising the step of preventing the display of said one fuel pressure signal on said oscilloscope to relate the displayed fuel injection pressure signals to their respective cylinders.

4. The diesel engine analyzer for synchronizing the pulses from an engine on an oscilloscope, wherein transducers monitor the pressures in the fuel injection lines of said engine and transmit signals to an oscilloscope represensative of the injection pressures for the cylinders of said engine,

the improvement which comprises, a motor, first means to derive from one of said transducers a signal to drive said motor at a speed proportional to the speed of said engine, and second means to generate oscilloscope reference pulses actuated by said motor.

5. The system of claim 4 wherein said motor is a synchronous motor, and wherein said first means cornprises means to amplify the signal from one of said transducers, means to generate first trigger pulses of a frequency representative of the speed of the fuel injection pump of said engine, means to generate second trigger pulses with a frequency representative of the speed of rotation of said injection pump and displaced in cornparison to said first trigger pulses,

wherein said first and second sets of pulses actuate said synchronous motor.

6. The system of claim 4 in which said means to generate oscilloscope reference pulses comprises disk means containing a series of trigger means which are suitably arranged circumferentially in groups of l, 2, 4, 6 and 8.

7. The system of claim 6 in which on one side of said trigger disk means a light source is positioned and on the other side of said trigger disk means suitably arranged adjacent to the circumferentially positioned trigger marks are photosensitive diodes.

8. The system of claim 7 in which said photosensitive diodes transmit reference pulses to said oscilloscope.

9. The system of claim 8 in which said photosensitive diodes are positioned in two groups radially spaced in respect to said trigger disk and mounted on movable supports.

10. The system of claim 9 in which one of the diodes on one of said movable supports is arranged to generate a vertical synchronization pulse once during each revolution of the trigger disk and the remaining diodes on said one support are postioned to generate either 2, 4, 6 or 8 pulses each revolution of the trigger disk to generate horizontal synchronization pulses.

11. The system of claim 9 wherein the diodes on the other of said second supports generates a number of reference pulses representative of the number of cylinders in the engine under investigation and wherein said reference pulses are transmitted to the Y input of said oscilloscope and to a stroboscope.

12. The system of claim 4 wherein said motor is a D.C. motor and wherein said first means comprises means for amplifying the signal from one of said transducers and means for generating a pulse train of constant amplitude and duration, and means responsive to said pulse train for driving said D C. motor at a speed proportional to the speed of said engine.

13. A circuit arrangement for displaying the injection pressures of diesel engines on an oscilloscope, being characterized by a piezoelectric transducer installed in the injection line of each cylinder, field effect transistor stages connected with each transducer, a differential amplifier jointly connected at its input with each field effect transistor Stage and connected at its output to the y input of the oscilloscope, a further field effect transistor stage conneced at its input with one of said transducers, a phase inverter connected at its input with said further field effect transistor stage, a Schmitt trigger with adjustable trigger level connected at its input with said phase inverter, a monostable vibrator actuated by said Schmitt trigger, a bistable vibrator actuated by said monostable vibrator, an integrator actuated by said bi-stable vibrator, a power amplifier actuated by said integrator and a synchronous motor actuated by said amplifier.

14. The system of claim 13 comprising a frequency doubling means actuated by said integrator, a second Schmitt trigger with adjustable trigger level actuated by said frequency doubling means, a second integrator actuated by said second Schmitt trigger, a third Schmitt trigger with adjustable trigger level actuated by said second integrator, second and third amplifying means respectively actuated by said second and third Schmitt triggers wherein the signals from said second and third amplifying means actuate said synchronous motor.

15. The system of claim 14 comprising at least one disk Ameans comprising trigger means arranged at the circumference at different diameters corresponding to the different number of cylinders in said engine, said disk being actuated by said synchronous motor, photocells actuated by said trigger disk and delivering at their output impulses for synchronizing image and lines on said oscilloscope, further photocells generating impulses for triggering a stroboscope and for gating in top dead center marks on said oscilloscope via the differential input of the y ampliiier, housing means for said photocells and said further photocells, which are mounted adjacent said trigger disk and which may be adjusted in order to vary the phase position of the impulses generated from said photocells.

16. In a system for displaying fuel injection line pressures of a diesel engine on an engine analyzer oscilloscope having vertical and horizontal synchronization inputs for synchronizing the fuel pressure displays with engine rotation, the combination comprising:

means for generating signals representative of the fuel injection line pressures and for applying said fuel injection line pressure signals to said oscilloscope, means responsive to one of said fuel injection line pressure signals for generating vertical and horizontal synchronization signals, and means for applying said vertical and horizontal synchronization signals to said vertical and horizontal inputs of said oscilloscope. 17. The system of claim .16 further comprising means for generating in response to said one fuel injection line pressure signal a pulse train comprising a number of pulses corresponding to the number of cylinders, and for ,applying said pulse train to said oscilloscope to display a representation of crank shaft position.

18. The system of claim 16 further including means for A preventing the display of said one fuel injection line pressure signal on said oscilloscope to relate the displayed fuel injection line pressure signals to their repective cylinders.

References Cited UNITED STATES PATENTS JERRY W. MYRACLE, Primary Examiner U.S. Cl. X.R. 73-119 

